Textural analysis of zircons is the first step of study that allows selection of targets for geochemical and isotope analysis (Hf isotopes, REE, 18O, etc.), which are necessary to understand geotectonic conditions of its formation and also its inheritance. Could someone want to tell me if the textural study of the core allows us to go so far as to determine if the zircon was detrital before receiving an overgrowth in, for example, a migmatite?
Estimado Dr. Masquelin:
It is difficult to give an all-embracing answer addressing the various phenomena in metamorphic, magmatic and sedimentary petrology.
Zircon pertain together with Ti oxides and tourmaline to the so-called ultrastable heavy minerals which are accumulated during hiatuses in sedimentation and as such may preserve such effects
1. If the alteration and grain morphology shows a position-related variation and intensity it points to a sedimentary effect
2. If a rim of minerals surrounds the nucleus, e.g., phyllosilicates it speaks in favor of sedimentary process
3. Are there any faces of the X affected more than others it can be due to a high-temperature fluid reaction rather than a supergene process
You might also have a look at my papers dealing with heavy minerals, predominantly with the zircon morphology.
Que tenga buena suerte!
H.G.Dill
Estimado Masquelin:
Como mencionan arriba, los cristales de circón son altamente resistentes a los procesos sedimentarios y únicamente experimentan redondeamiento cuando han sido expuestos a un largo proceso de transporte o a más de un ciclo sedimentario. En el caso de los cristales formados a partir de fluidos anatécticos o magmas se observa que los cristales crecen preferentemente a lo largo del eje mayor, esto es, son delgados y alargados generalmente, y sus caras están perfectamente definidas. Mediante imágenes de CL podrás ver la morfología de los cristales y discriminarlos.
Hay algunos trabajos clásicos sobre texturas en cristales de circón. Abajo te dejo algunos de los que he leído:
1.- Zircon and Granite Petrology - Pupin (1980)
2.- Corfu, F., Hanchar, J. M., Hoskin, P. W. O., & Kinny, P. (2003). Atlas of Zircon Textures.
3.- Watson, E. B. (1996). Dissolution, growth and survival of zircons during crustal fusion: kinetic principles, geological models and implications for isotopic inheritance.
Saludos
Román
Hola Henri, if the zircons that you are dating are from a migmatite you need to establish if the zircons are from the neosome or the paleosome, if they are from the neosome the zircons could be zoned or unzoned but it is probably that they doesnt present difference in the age. But if they are from a pelitic paleosome it is probably that you will find a diference of age in the core.
Te anexo una imagen de unos zircones provenientes del neosoma tonalítico de una metatexita con protolito de anfibolita, donde datamos tanto los margenes como los nucleos de varios circones zonados, al final las edades resultaron las mismas en todas las partes de los circones, además no hay mucha investigación sobre circones en neosomas, los circones del paleosoma te van a registrar la información sobre todos los procesos que sufrio esa roca durante el metamorfismo hasta la fusión parcial. Si necesitas algunos artículos sobre eso, dame tu correo y te los envío!
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